When charging refrigerant in air conditioning systems, inaccurate measuring how much refrigerant enters an air conditioning system during a charge can effect the air conditioning system performance. Charging machines (sometimes called recovery units) are often used to charge air conditioning systems.
After charging some air conditioning systems, the high side service hose of a charging unit may be filled with high-pressure liquid refrigerant. Disconnecting the hose while it is full of refrigerant may cause the system being serviced to be undercharged which can result in poor air conditioning system performance.
Accordingly, it is desirable to provide a method and apparatus that allows refrigerant from the high side hose of the charging unit to equalize (thus causing refrigerant from the high side of the system to enter the air conditioning system) with the low side of the air conditioning system before the low side hose is removed from the air conditioning system.